1. Field of the Invention
The invention relates to a method for the self-cleaning of a cleaning machine, in particular a continuous dishwasher for items to be cleaned, such as for example crockery.
2. Description of the Background Art
Cleaning machines, in particular continuous dishwashers, which are used for example for cleaning the crockery, tray and container parts to be cleaned that arise in communal catering, are known. Whereas dishwashing devices for the domestic sector generally pass through a program sequence with the successive cleaning steps in a stationary arrangement of the crockery and cutlery parts to be cleaned, the treatment zones in continuous dishwashers are arranged one after another and the items for rinsing or the items to be cleaned are transported by means of a conveyor from the loading region (inlet region), through treatment zones to be passed through in succession, to the removal region (outlet region).
Continuous dishwashers known in the prior art generally have four different treatment zones between the inlet region and outlet region. A conveyor conveys the items for rinsing through the individual treatment zones. The treatment zones are a pre-cleaning zone, at least one cleaning zone, a clear rinsing zone and also a drying zone. In the cleaning zone, loosely clinging dirt is removed from the items to be cleaned. For this purpose, rinsing liquid is drawn through a pump from the storage tank associated with this treatment zone and sprayed over the items to be cleaned through suitably embodied nozzles. Subsequently, the rinsing liquid flows back into the storage tank again, where it is drawn in again by a circulating pump and introduced into a circulating circuit. Conventionally, the storage tank is covered by strainers in order to keep relatively large dirt particles out of the rinsing liquid.
In the at least one cleaning zone adjoining the pre-cleaning zone, dirt particles still clinging to the items for rinsing to be cleaned are removed by means of a conventionally alkaline rinsing liquid. For this purpose, the heated rinsing liquid is drawn out of the storage tank associated with the treatment zone through a further circulating pump and sprayed over the items for rinsing by means of suitably positioned and oriented nozzles. Subsequently, the rinsing liquid flows back into the corresponding storage tank again, where it is drawn in again by the circulating pump. Conventionally, the storage tank is covered by strainers in order to prevent relatively coarse dirt particles from entering the rinsing liquid.
In the clear rinsing zone adjoining the at least one cleaning zone, the alkaline rinsing liquid, which wets the surface of the items for rinsing, is rinsed away together with any remaining food remnants from the surface of the items for rinsing by means of hot fresh water to which a clear rinsing aid is generally added. In specific embodiments of the clear rinsing zone, the fresh water is again collected after this treatment step in a storage tank associated with this treatment zone and drawn in using a circulating pump associated with this treatment zone and distributed over the items for rinsing by the actual fresh water clear rinsing by means of nozzles (pump clear rinsing). Subsequently, the rinsing liquid flows back into the storage tank again, where it is drawn in again by the circulating pump.
The volume of water that is supplied to the described dishwasher in the clear rinsing zone flows over by means of overflows, merely as a result of the action of gravity between the storage tanks of the individual zones, in each case from zone to zone and in this way renews the contents of each of the storage tanks. An overflow, which guides the excess water to the channel system, is located in the first tank of the machine (pre-rinsing zone). Each storage tank comprises a suitable means, i.e. for example a manually operable drain valve which serves to empty each storage tank.
DE 10 2005 008987 B3, which corresponds to U.S. Publication No. 2008/0041419, and which is incorporated herein by reference, discloses a dishwasher having in each treatment zone, in relation to the above-described embodiment, a filter that is used to continuously filter the cleaning fluid located in the respective storage tank. In addition, this design of a dishwasher has pumps between the individual storage tanks of the respective zones, so that the water which is supplied to the dishwasher in the clear rinsing can be pumped into the storage tank of the further treatment zones in a controlled and targeted manner. In addition, each of the storage tanks of this machine has its own electrically driven component for emptying the tank, i.e. a pump.
At the end of an operating cycle, i.e. for example at the end of a working day, the above-described dishwashers are generally emptied and thoroughly cleaned. This is necessary in order to allow hygienic operation of the dishwasher. This cleaning is normally carried out in such a way that the doors or flaps with which each treatment zone is equipped are opened. The storage tank of each zone is then emptied using the means provided for this purpose, i.e. for example using the manual drain valves or if appropriate the pumps. Furthermore, all the strainers are removed from the tanks and cleaned by hand outside the machine using water. The interior of the individual treatment zones is generally sprayed out and rinsed out with water by hand with the aid of a hose with a spraying device. Dirt, i.e. for example food remnants, starch deposits and rims of fat, etc. which have accumulated in the interior of the zones during the rinsing operation, are removed in this way and rinsed into the channels through the outflow openings of the individual storage tanks. The water which is used for this purpose is generally tap water, optionally heated tap water, without the addition of cleaning agents.
A drawback of a conventional procedure reside in the fact that thorough cleaning and rinsing-out of the individual treatment zones of the dishwashers uses up a large amount of fresh water. This is due partly to the fact that water is conventionally used without the addition of cleaning agents and the dirt in the treatment zones at the end of a day contains for example also fat-type components which have to be rinsed away. This additionally promotes the above-described consumption of fresh water. The quality of the cleaning carried out in this way is very highly dependent on the person performing the task, i.e. on how conscientiously he carries out the cleaning. In order to perform the activity or to visually inspect the result of the cleaning, the cleaner has to bend or squeeze into the respective treatment zone through the door of the dishwasher; this is not advantageous for ergonomic reasons.
As a manual cleaning requires the doors of the individual treatment zones to be left open and these doors are very frequently embodied as upwardly movable sliding doors, the back or the inner side of these doors cannot be sprayed down; instead, the back or the inner side of doors of this type is very difficult to clean. Depending on the manner in which the jet of water from the spraying device strikes walls or built-in parts in the treatment zone, this jet is reflected and sprays back in the direction of the cleaner, as a result of which, viewed globally, the result of the conventional cleaning process to be carried out by hand is, after the end of the working day, highly dependent on subjective influences, very inconvenient to carry out and is above all very time-consuming.
Solutions are known in which attempts are made, by way of additional equipment measures, to eliminate or at least to alleviate the drawbacks outlined hereinbefore. Thus, for example, a solution is known according to which a nozzle system, which is fed via a separate pump, is arranged on the ceiling of each storage tank. The separate pump is supplied from the pump clear rinsing storage tank. This water is still relatively clean even at the end of a working day. While or after the water is let out or pumped out from the remaining storage tanks, the water from the pump clear rinsing storage tank can now be used to spray down the ceilings of the storage tanks. The dripping water is then no longer collected, but runs in the channels. The drawback of this procedure resides in the fact that the amount of water in the pump clear rinsing storage tank is highly limited. The pump clear rinsing storage tank conventionally has merely a volume of about 30 l, so that the automated cleaning effect is also extremely limited as a result of the one-off use of this amount.
Furthermore, solutions are known that seek to reduce the drawbacks described hereinbefore by way of additional procedural measures. Thus, there are for example machines in which, after the above-described manual emptying and initial cleaning of the strainers, the tanks of the machine are refilled, heated up and enriched with cleaner. In the machine, which is reprepared in this way for operation using clean water, the circulating pumps of all the tanks are started up again and the inner side of the machine is sprayed down with clean washing liquor. The drawback of this procedure resides in the fact that a very large amount of additional water, cleaner and energy has to be used up in order to reprepare for operation the machine as a whole at the end of an operating cycle. In addition, the filling and heating-up of the storage tanks takes a relatively long time. In the region of the pre-cleaning zone, the cleaning effect will be insufficient using this method, as on the one hand most dirt accumulates here as a result of the operation and on the other hand this zone conventionally has neither a possibility for heating-up nor a possibility for adding cleaners.